Method and device for obtaining secondary timing advance

ABSTRACT

Embodiments of the present invention provide a method and a device for obtaining a secondary timing advance. The method includes: after a secondary cell activation command is received or after a secondary cell is activated, if a secondary time alignment timer TAT of the secondary cell does not run, initiating, by a terminal, a random access procedure; and obtaining, by the terminal, the secondary TA according to a TA received in the random access procedure. With the method and the device for obtaining a timing advance according to embodiments of the present invention, a terminal initiates a random access procedure to obtain a secondary timing advance after the terminal receives a secondary cell activation command sent by a base station or after a secondary cell is activated, thereby saving signaling overhead and system resources.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/299,274, filed on Oct. 20, 2016, which is a continuation of U.S.patent application Ser. No. 14/874,163, filed on Oct. 2, 2015, now U.S.Pat. No. 9,491,778, which is a continuation of U.S. patent applicationSer. No. 14/041,829, filed on Sep. 30, 2013, now U.S. Pat. No.9,185,611, which is a continuation of International Application No.PCT/CN2012/073469, filed on Apr. 1, 2012. The International Applicationclaims priority to Chinese Patent Application No. 201110084167.7, filedon Apr. 2, 2011. All of the afore-mentioned patent applications arehereby incorporated by reference in their entireties.

TECHNICAL FIELD

The present invention relates to the field of communicationtechnologies, and in particular, to a method and a device for obtaininga secondary timing advance.

BACKGROUND

A long term evolution (Long Term Evolution, LTE) system is anext-generation wireless communication standard being formulated by the3rd generation partnership project (The 3rd Generation PartnershipProject, 3GPP). It has advantages such as high spectrum utilization andtransmission speed, and low transmission delay. The terminal of an LTEsystem implements uplink transmission synchronization with a basestation by using a timing advance (Timing Advance, TA), and maintainsuplink synchronization by using a time alignment timer (Time AlignmentTimer, TAT). With the introduction of a TA, uplink transmission of allterminals can be accomplished at the time expected by the base station,thereby avoiding collision between terminals during the uplinktransmission and implementing time division multiplexing.

To provide a higher data rate, the base station may configure, for theterminal, one or more secondary cells (Secondary Cells, SCells) toassist a primary cell (Primary Cell, PCell) in data transmission. Theprimary cell and secondary cells correspond to an uplink carrier each,where transmission over different uplink carriers may need to usedifferent TAs. The TA corresponding to a primary cell is known as aprimary TA, and the TAT corresponding to a primary cell is known as aprimary TAT; the TA corresponding to a secondary cell is known as asecondary TA, and the TAT corresponding to a secondary cell is known asa secondary TAT.

In the prior art, after a secondary cell is configured, if the secondarycell does not use an existing TA of a primary cell, a terminal obtains asecondary TA of the secondary cell by initiating random access in thesecondary cell. This may increase signaling overhead in a random accessprocedure and a TA maintenance procedure and waste system resources.

SUMMARY

Embodiments of the present invention provide a method and a device forobtaining a secondary timing advance, which can reduce signalingoverhead and save system resources during the obtaining of the secondaryTA.

An embodiment of the present invention provides a method for obtaining asecondary timing advance, including:

after a secondary cell activation command is received or after asecondary cell is activated, if a secondary time alignment timer TAT ofthe secondary cell does not run, initiating, by a terminal, a randomaccess procedure; and

obtaining, by the terminal, a secondary timing advance TA of thesecondary cell according to a TA received in the random accessprocedure.

An embodiment of the present invention provides another method forobtaining a secondary timing advance, including:

sending a secondary cell activation command to a terminal; and sending aTA to the terminal in a random access procedure according to randomaccess initiated by the terminal, where the random access is initiatedby the terminal if a secondary TAT of a secondary cell does not runafter the terminal receives the secondary cell activation command orafter it is confirmed according to the secondary cell activation commandthat the secondary cell is activated.

An embodiment of the present invention provides a method for processinguplink out-of-synchronization. The method includes: starting, by aterminal, a secondary TAT of a configured secondary cell; and, if theTAT of the secondary cell expires, notifying, by the terminal, a basestation, and/or stopping uplink transmission on the secondary cell,and/or activating the secondary cell.

An embodiment of the present invention provides a terminal, including:

a receiving unit, configured to receive a secondary cell activationcommand;

a random access unit, configured to initiate a random access procedureif a secondary time alignment timer TAT of a secondary cell does not runafter the receiving unit receives the secondary cell random accesscommand or after the secondary cell is activated; and

an obtaining unit, configured to obtain a secondary timing advance TA ofthe secondary cell according to a TA received in the random accessprocedure.

An embodiment of the present invention provides a base station,including:

a first sending unit, configured to send a secondary cell activationcommand to a terminal; and

a second sending unit, configured to send a TA to the terminal in arandom access procedure according to random access initiated by theterminal, where the random access is initiated by the terminal if asecondary TAT of a secondary cell does not run after the terminalreceives the secondary cell activation command or after it is confirmedaccording to the secondary cell activation command that the secondarycell is activated.

An embodiment of the present invention provides a terminal, including: astarting unit, configured to start a secondary TAT according to anobtained secondary TA; and a processing unit, configured to: if thesecondary TAT expires, notify expiry of the secondary TAT to a basestation, and/or stop uplink transmission on a secondary cellcorresponding to the secondary TAT, and/or deactivate the secondary cellcorresponding to the secondary TAT.

With the method and the device for obtaining a secondary timing advanceaccording to embodiments of the present invention, a terminal initiatesa random access procedure to obtain a secondary timing advance after theterminal receives a secondary cell activation command or after asecondary cell is activated, thereby saving signaling overhead andsystem resources.

BRIEF DESCRIPTION OF DRAWINGS

To illustrate the technical solutions in the embodiments of the presentinvention more clearly, the following briefly introduces theaccompanying drawings required for describing the embodiments.Apparently, the accompanying drawings in the following description showmerely some embodiments of the present invention, and a person ofordinary skill in the art may still derive other drawings from theseaccompanying drawings without creative efforts.

FIG. 1 is a flowchart of a method for obtaining a secondary timingadvance according to an embodiment of the present invention;

FIG. 2 is a flowchart of a method for obtaining a secondary timingadvance according to another embodiment of the present invention;

FIG. 3 is a flowchart of a method for obtaining a secondary timingadvance according to still another embodiment of the present invention;

FIG. 4 is a flowchart of a method for obtaining a secondary timingadvance according to still another embodiment of the present invention;

FIG. 5 is a flowchart of a method for obtaining a secondary timingadvance according to still another embodiment of the present invention;

FIG. 6 is a flowchart of a method for obtaining a secondary timingadvance according to still another embodiment of the present invention;

FIG. 7 is a schematic diagram of obtaining a secondary TA in anembodiment provided in FIG. 6;

FIG. 8 is a flowchart of a method for obtaining a secondary timingadvance according to still another embodiment of the present invention;

FIG. 9 is a schematic diagram of obtaining a secondary TA in anembodiment provided in FIG. 8;

FIG. 10 is a flowchart of a method for processing uplinkout-of-synchronization according to an embodiment of the presentinvention;

FIG. 11 is a schematic structural diagram of a terminal according to anembodiment of the present invention;

FIG. 12 is a schematic structural diagram of a terminal according toanother embodiment of the present invention; and

FIG. 13 is a schematic structural diagram of a base station according toan embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

To make the objectives, technical solutions, and advantages of theembodiments of the present invention more comprehensible, the followingclearly and describes the technical solutions in the embodiments of thepresent invention with reference to the accompanying drawings in theembodiments of the present invention. Apparently, the describedembodiments are merely a part rather than all of the embodiments of thepresent invention. All other embodiments obtained by a person ofordinary skill in the art based on the embodiments of the presentinvention without creative efforts shall fall within the protectionscope of the present invention.

In embodiments of the present invention, a base station may be anevolved NodeB (evolved NodeB, eNB), a base station (Base Station, BS), aNode B, an access point (access point), or the like. The base stationmay be a macro base station, or a medium base station, or a micro basestation such as a home base station. Each base station is capable ofproviding communication coverage for a specific geographic area. A term“cell (cell)” may be a coverage area of a base station, and/or acoverage area served by a base station subsystem, depending on thecontext where the term is used. A base station is capable of providingcommunication coverage for macro cells, pico cells (pico cells), femtocells (femto cells), and/or cells of other types.

In embodiments of the present invention, terminals may be distributed inan entire wireless network. Each terminal may be static or moving. Aterminal (terminal) may be a user equipment (user equipment, UE), amobile station (mobile station, MS), a subscriber unit (subscriberunit), a station (station), or the like. The terminal may also be acellular phone (cellular phone), a personal digital assistant (personaldigital assistant, PDA), a modem (modem), a wireless communicationdevice, a handheld device (handheld), a laptop computer (laptopcomputer), a cordless phone (cordless phone), a wireless local loop(wireless local loop, WLL) station, or the like. The terminal is capableof communicating with a base station such as a macro base station, apico base station, and a femto base station. The terminal may also be acommunication device that communicates with a base station and plays arole similar to a terminal. For example, during initial network access,a relay node(relay node, RN) accesses a network as a terminal when theRN communicates with a base station.

FIG. 1 is a flowchart of a method for obtaining a secondary timingadvance according to an embodiment of the present invention. As shown inFIG. 1, the method includes the following:

S101. After a terminal receives a secondary cell activation command orafter a secondary cell is activated, if a secondary TAT of the secondarycell does not run, the terminal initiates a random access procedure,where the secondary TA of the secondary cell is different from a primaryTA of a primary cell.

S102. The terminal obtains the secondary TA according to a TA receivedin the random access procedure.

A base station may carry a TA in a message 2 of the random accessprocedure sent to the terminal. After obtaining the TA, the terminal maystart a TAT. During TAT running, the terminal is in an uplinksynchronization state. In the embodiment of the present invention, thefollowing may be further included: calibrating, by the base station, theTA by sending the timing advance command (Timing Advance Command) of amedia access control (Medium Access Control, MAC) layer so that uplinktransmission of the terminal is synchronized with the base station. Theterminal restarts the TAT according to the calibrated TA value receivedin the TA command so that uplink transmission is synchronized with thebase station.

In the embodiment of the present invention, the terminal receives thesecondary cell activation command, where the secondary cell may havebeen activated or not have been activated. After receiving the secondarycell activation command, the terminal may, no matter whether thesecondary cell has been activated or not, initiate a random accessprocedure if the secondary TAT of the secondary cell does not run. Or,after receiving the secondary cell activation command, the terminal mayconfirm that the secondary cell has been activated, and then initiate arandom access procedure if the secondary TAT of the secondary cell doesnot run.

In this embodiment, the secondary TA of the secondary cell and theprimary TA of the primary cell may be different, that is, they do notbelong to the same TA group (TA Group, TAG). When there are multiplesecondary cells, the secondary TAs of these secondary cells may bedifferent from the primary TA of the primary cell. Additionally, thesecondary TAs of these secondary cells may be the same. For example, ifa secondary cell with a secondary TA different from the primary TA ofthe primary cell has a physical random access channel (Physical RandomAccess Channel, PRACH) resource, the terminal may use the secondary cellhaving the PRACH resource as a reference cell and initiate a randomaccess procedure on this secondary cell. When there are multiplesecondary cells with secondary TAs different from the primary TA of theprimary cell, and the secondary TAs of the multiple secondary cells arethe same, if at least one secondary cell among these secondary cells hasa PRACH resource, the terminal may use the secondary cell having thePRACH resource as a reference cell and initiate a random accessprocedure on this secondary cell. The function of a reference cell isthat during initiation of the random access procedure by the terminal,reference is made to a downlink carrier of the reference cell when theterminal sends a preamble (preamble).

In an embodiment of the present invention, after a terminal receives asecondary cell activation command or after a secondary cell isactivated, if a secondary TAT of the secondary cell does not run, theterminal may initiate a random access procedure to obtain the secondaryTA of the secondary cell. The terminal may immediately initiate a randomaccess procedure actively if the secondary TAT of the secondary celldoes not run after the secondary cell activation command is received orafter the secondary cell is activated. Or, the terminal may not initiaterandom access actively, but initiate random access when triggered by abase station. For example, after the secondary cell activation commandis received or after the secondary cell is activated, if the secondaryTAT of the secondary cell does not run, the terminal may initiate arandom access procedure according to a random access command afterreceiving the random access command. If the random access command sentby the base station specifies a reference cell, the terminal mayinitiate, according to the specified reference cell, the random accessprocedure on a secondary cell having a PRACH resource (that is, duringinitiation of random access by the terminal, reference is made to adownlink carrier of the reference cell specified by the base station,when the terminal sends a preamble). If the random access command doesnot specify a reference cell, the terminal may use the cell carrying therandom access command as a reference cell, and initiate a random accessprocedure on the cell carrying the random access command. In anembodiment of the present invention, the terminal may also set a randomaccess timer. In the case that the secondary TAT of the secondary celldoes not run after a secondary cell activation command is received orafter a secondary cell is activated, the terminal may initiate randomaccess according to the reference cell specified in a random accesscommand if a random access command is received within a duration set bythe random access timer, or initiate a random access procedure on a cellcarrying the random access command; if a random access command is notreceived within a duration set by the random access timer, the terminalmay use the secondary cell as a reference cell and initiate a randomaccess procedure on this secondary cell. That is, with the random accesstimer, the terminal first waits for a period set by the random accesstimer. If a random access command is received within the set period, theterminal initiates a random access procedure according to the randomaccess command; if a random access command is not received within theset period, the terminal initiates a random access command after the setperiod expires.

When the terminal initiates random access on the secondary cell toobtain the secondary TA, the secondary TA may be a TA received by theterminal in the random access procedure. For example, the base stationmay send a message 2 (message 2) of the random access procedure, namely,a response message of the random access procedure, to the terminal inthe random access procedure, where the message 2 carries a TA.Understandably, in an embodiment of the present invention, a basestation may also carry a TA in another message sent to the terminal inthe random access procedure.

Additionally, in the embodiment of the present invention, the terminalmay use the primary cell as a reference cell and initiate a randomaccess procedure on a secondary cell. In this case, the secondary TAobtained by the terminal may not be the TA sent in the random accessprocedure. The secondary TA obtained by the terminal may be a sum of thesecondary TA sent by the base station, which is a TA received in therandom access procedure, and a difference between a downlink carriertiming value of the secondary cell and a downlink carrier timing valueof the primary cell. Or, the secondary TA obtained by the terminal maybe a difference between twice the TA received in the random accessprocedure and the TA of the primary cell. Similarly, the base stationmay carry a TA in the message 2 of the random access procedure sent tothe terminal in the random access procedure, or carry a TA in anothermessage sent to the terminal in the random access procedure.

In an embodiment of the present invention, when none of the secondarycells of the terminal has a PRACH resource, the terminal may use asecondary cell as a reference cell and initiate a random accessprocedure on the primary cell. In this case, the secondary TA obtainedby the terminal may be a sum of the TA sent by the base station in therandom access procedure and a difference between a downlink carriertiming value of the secondary cell and a downlink carrier timing valueof the primary cell; or, the secondary TA obtained by the terminal maybe a difference between twice the TA received in the random accessprocedure and the TA of the primary cell.

In the method for obtaining a secondary timing advance according to thisembodiment, when the secondary TA of the secondary cell needs to beobtained, the terminal may, instead of initiating a random accessprocedure arbitrarily, initiate a random access procedure to obtain thesecondary timing advance after a secondary cell activation command isreceived or after a secondary cell is activated. This can avoidunnecessary signaling overhead and system resource waste in the randomaccess procedure and a TA maintenance procedure when the secondary cellis in a deactivated state, thereby saving signaling overhead and systemresources.

FIG. 2 is a flowchart of a method for obtaining a secondary timingadvance according to another embodiment of the present invention. Asshown in FIG. 2, the method includes the following:

S201. Send a secondary cell activation command to a terminal.

S202. Send a TA to the terminal in a random access procedure accordingto random access initiated by the terminal, where: the random access isinitiated by the terminal if a secondary TAT of a secondary cell doesnot run after a secondary cell activation command is received or afterit is confirmed according to the secondary cell activation command thatthe secondary cell is activated; and a secondary TA of the secondarycell is different from a primary TA of a primary cell.

In this embodiment, a TA is sent to the terminal through the randomaccess procedure so that the terminal obtains the secondary TA.

The executor of the above steps may be a base station.

In the embodiment of the present invention, the base station sends asecondary cell activation command to the terminal, and the terminal mayinitiate a random access procedure to obtain the secondary TA of thesecondary cell if the secondary TAT of the secondary cell does not runafter the secondary cell activation command is received or after thesecondary cell is activated.

In this embodiment, the terminal may use a secondary cell having a PRACHresource as a reference cell and initiate a random access procedure onthe secondary cell. The secondary TA obtained by the terminal may be aTA sent to the terminal by the base station in the random accessprocedure. Or, the terminal may use the primary cell as a reference celland initiate a random access procedure on the secondary cell. Or, whennone of the secondary cells of the terminal has a PRACH resource, theterminal may use a secondary cell as a reference cell and initiate arandom access procedure on the primary cell. In this embodiment, for theterminal to initiate a random access procedure, reference may be made tothe method embodiment shown in FIG. 1.

FIG. 3 is a flowchart of a method for obtaining a secondary timingadvance according to still another embodiment of the present invention.As shown in FIG. 3, after a secondary cell activation command isreceived or after a secondary cell is activated, if a secondary TAT ofthe secondary cell does not run, the terminal uses the secondary cell asa reference cell and initiates a random access procedure on thesecondary cell to obtain the secondary TA of the secondary cell. Itshould be noted that, for multiple secondary cells with the samesecondary TA, at least one secondary cell should have a PRACH resourceso that the terminal may initiate a random access procedure on thesecondary cell having a PRACH resource.

S301. A base station configures multiple secondary cells for a terminal.

In this embodiment, for example, there are two secondary cells: SCell1and SCell2; SCell1 and a primary cell belong to the same TA group, TAG1;and SCell2 belongs to another TA group, TAG2. Because SCell2 does notuse the primary TA, the terminal needs to obtain a secondary TAcorresponding to SCell2, that is, TA2. Additionally, the base stationmay indicate that SCell2 has a PRACH resource.

S302. The terminal receives a secondary cell activation command sent bythe base station.

For example, the base station may carry the secondary cell activationcommand in an activation/deactivation MAC controlelement(Activation/Deactivation MAC Control Element).

This secondary cell activation command may be used to activate bothsecondary cells SCell1 and SCell2.

S303. The terminal uses SCell2 as a reference cell and initiates arandom access procedure on a PRACH of SCell2.

After activating SCell2, if the terminal finds that the secondary TAT ofSCell2, TAT2, does not run, the terminal may initiate a random accessprocedure to obtain the secondary TA of SCell, namely, TA2. The terminaluses SCell2 as a reference cell, that is, the terminal uses a downlinkcarrier of SCell2 for reference. When the terminal selects a PRACH of anuplink subframe n of SCell2 to send a preamble, the time when thepreamble starts to be sent is the time when a downlink subframe ncorresponding to the SCell2 starts to be received, where n may be anon-negative integer identifying a subframe, or may be a symbol or acharacter that is used to identify the subframe.

S304. The terminal obtains a secondary TA according to a message in therandom access procedure.

The terminal receives a message 2 of the random access procedure sent bythe base station, where the message 2 of the random access procedurecarries a TA. Then, TA2 obtained by the terminal may be the TA carriedin the message 2 so that the terminal may start the TAT2.

In this embodiment, the process for obtaining a secondary TA of thesecondary cell SCell2, which does not use the primary TA, is provided.If the base station also configures, for the terminal, another secondarycell that belongs to the same TA group as SCell2, a TA of anothersecondary cell can be obtained by using the method provided in thisembodiment. If the base station also configures, for the terminal,another secondary cell that does not belong to the same TA group asSCell2, when the corresponding secondary TAT does not run after theanother secondary cell is activated, the terminal also needs to initiatea random access procedure on a secondary cell having a PRACH resource toobtain the secondary TA corresponding to the another secondary cell.

It should be noted that in this embodiment, when the terminal activelyinitiates a random access procedure, the terminal needs to contend for aPRACH resource with other terminals. Therefore, the random accessprocedure may fail. If the terminal fails to initiate a random accessprocedure, the terminal may continue to use SCell2 as a reference celland initiate a random access procedure on the PRACH of SCell2 until therandom access succeeds or the number of random access attempts exceeds amaximum value.

FIG. 4 is a flowchart of a method for obtaining a secondary timingadvance according to still another embodiment of the present invention.As shown in FIG. 4, in this embodiment, after a secondary cellactivation command is received or after a secondary cell is activated,if a secondary TAT of the secondary cell does not run, the terminal doesnot immediately initiate random access. Instead, after the terminalreceives a random access command sent by a base station, the terminalmay use a cell carrying the random access command as a reference celland initiate a random access procedure on this reference cell to obtaina secondary TA of the secondary cell. It should be noted that thesecondary cell carrying the random access command has a PRACH resourceso that the terminal may initiate a random access procedure on thesecondary cell.

S401. A base station configures a secondary cell for a terminal.

In this embodiment, the base station may configure a secondary cellSCell1 for the terminal, and indicate that SCell1 does not belong to thesame TA group as a primary cell PCell but belongs to another TA group,TAG2. Additionally, the base station indicates that SCell1 has a PRACHresource.

S402. The terminal receives a secondary cell activation command sent bythe base station.

This command is used to activate the secondary cell SCell1.

S403. The terminal receives a random access command on SCell1.

The random access command received by the terminal may be, for example,a physical downlink control channel order (Physical Downlink ControlChannel Order, PDCCH order).

Because the base station indicates that SCell1 has a PRACH resource, thebase station may use a random access command to trigger the terminal toinitiate a random access procedure on SCell1.

S404. The terminal uses SCell1 as a reference cell and initiates arandom access procedure on SCell1.

S405. The terminal obtains a secondary TA according to a message in therandom access procedure.

The terminal receives a message 2 of the random access procedure sent bythe base station, where the message 2 of the random access procedurecarries a TA. The secondary TA of the Scell obtained by the terminal isthe TA carried in the message 2 so that the terminal may start asecondary TAT corresponding to the SCell.

FIG. 5 is a flowchart of a method of obtaining a secondary timingadvance according to still another embodiment of the present invention.As shown in FIG. 5, in this embodiment, after a secondary cellactivation command is received or after a secondary cell is activated,if a secondary TAT of the secondary cell does not run, a terminal startsa random access timer. If, before the random access timer expires, theterminal receives a random access command used to obtain a TA of thesecondary cell and sent by a base station, the terminal stops the timer,and initiates, according to the random access command sent by the basestation, random access on a secondary cell carrying the command or acell specified in the random access command; if, before the randomaccess timer expires, the terminal does not receive a random accesscommand sent by the base station, the terminal may use the secondarycell as a reference cell and initiate a random access procedure toobtain a corresponding TA under a prerequisite that the secondary cellfor initiating a random access procedure has a PRACH resource.

S501. A base station configures a secondary cell for a terminal.

In this embodiment, the base station may configure a secondary cellSCell1 for the terminal, and indicate that SCell1 does not belong to thesame TA group as a primary cell PCell but belongs to another TA group,TAG2. Additionally, the base station indicates that SCell1 has a PRACHresource.

S502. After the terminal receives a secondary cell activation commandsent by the base station or after the secondary cell is activated, theterminal starts a random access timer.

The secondary cell activation command is used to activate the secondarycell SCell1.

S503. Before the random access timer expires, if the terminal does notreceive, on SCell1, a random access command sent by the base station,the terminal uses SCell1 as a reference cell and initiates a randomaccess procedure on SCell1.

S504. The terminal receives a message of the random access proceduresent by the base station and obtains a secondary TA.

The terminal receives a message 2 of the random access procedure sent bythe base station, where the message 2 of the random access procedurecarries a TA. The secondary TA of the Scell obtained by the terminal maybe the TA carried in the message 2 so that the terminal may start asecondary TAT corresponding to the Scell.

It should be noted that if, before the random access timer expires, theterminal receives a random access command sent by the base station forTAG2, and if the random access command clearly specifies the referencecell or the TA that needs to be obtained, the terminal may use the cellspecified in the random access command as a reference cell, and initiatea random access procedure on a secondary cell corresponding to thesecondary TA that needs to be obtained to obtain the TA, under theprerequisite that the secondary cell for initiating the random accessprocedure has a PRACH resource. If the random access command does notclearly specify the reference cell, the terminal may use the cellcarrying the random access command as a reference cell and initiate arandom access procedure on the reference cell to obtain the secondaryTA.

FIG. 6 is a flowchart of a method for obtaining a secondary timingadvance according to still another embodiment of the present invention.As shown in FIG. 6, in this embodiment, after a secondary cellactivation command is received or after a secondary cell is activated,the secondary cell does not have a PRACH resource. If a secondary TAT ofthe secondary cell does not run, a terminal may use the secondary cellas a reference cell and initiate a random access procedure on a primarycell to obtain a TA, where, secondary TA=TA_msg2+delta or2*TA_msg2−TA_pcell. TA_msg2 is a TA carried in a message 2 of the randomaccess procedure; delta is a difference between a downlink carriertiming value of a secondary cell and a downlink carrier timing value ofa primary cell; and TA_pcell is a TA of the primary cell.

S601. A base station configures a secondary cell for a terminal.

In this embodiment, the base station configures a secondary cell SCell1for the terminal, and indicates that SCell1 does not belong to the sameTA group as a primary cell PCell but belongs to another TA group, TAG2.

S602. The terminal receives a secondary cell activation command sent bythe base station.

This secondary cell activation command may be used to activate thesecondary cell SCell1.

S603. The terminal uses SCell1 as a reference cell and initiates arandom access procedure on the primary cell PCell.

After the terminal receives the secondary cell activation command sentby the base station or after the SCell1 is activated, if the terminalfinds that a secondary TAT of SCell1 does not run, the terminal mayinitiate a random access procedure to obtain the secondary TA of Scell.The terminal uses SCell1 as a reference cell, that is, the terminal usesa downlink carrier of SCell1 for reference. When the terminal selects aPRACH of an uplink subframe n of PCell to send a preamble, the time whenthe preamble starts to be sent is the time when a downlink subframe ncorresponding to SCell1 starts to be received, where n may be anon-negative integer identifying a subframe or may be a symbol or acharacter that is used to identify the subframe.

S604. The terminal receives a message of the random access proceduresent by the base station and obtains a secondary TA.

The terminal receives the message 2 of the random access procedure sentby the base station, and calculates the secondary TA of according to aTA carried in the message 2 of the random access procedure so that thesecondary TAT of Scell may be started.

FIG. 7 is a schematic diagram of obtaining a secondary TA according toan embodiment provided in FIG. 6. FIG. 7 shows a method for calculatingTA2.

In FIG. 7, Msg1 is a message 1 (message 1) in the random accessprocedure, where the message 1 may include a preamble; and an eNB is anevolved base station (evolved NodeB).

TA2=TA_msg2+delta or TA2=2×TA_msg2−TA_pcell, where, TA_msg2 is a TAcarried in a message 2 of the random access procedure; delta is adifference between a downlink carrier timing value of a secondary celland a downlink carrier timing value of a primary cell; and TA_pcell is aTA of the primary cell.

FIG. 8 is a flowchart of a method for obtaining a secondary timingadvance according to still another embodiment of the present invention.As shown in FIG. 8, in this embodiment, after a secondary cellactivation command is received or after a secondary cell is activated,if a secondary TAT of the secondary cell does not run, the terminal usesa primary cell as a reference cell and initiates a random accessprocedure on the secondary cell to obtain a TA. SecondaryTA=TA_msg2+delta or 2*TA_msg2−TA_pcell, where, TA_msg2 is a TA carriedin a message 2 of the random access procedure; delta is a differencebetween a downlink carrier timing value of a secondary cell and adownlink carrier timing value of a primary cell; and TA_pcell is a TA ofthe primary cell.

S701. A base station configures a secondary cell for a terminal.

In this embodiment, the base station may configure a secondary cellSCell1 for the terminal, and indicate that the SCell1 does not belong tothe same TA group as a primary cell PCell but belongs to another TAgroup, TAG2.

S702. The terminal receives a secondary cell activation command sent bythe base station.

This command is used to activate the secondary cell SCell1.

S703. The terminal uses the primary cell PCell as a reference cell andinitiates a random access procedure on SCell1.

After the terminal receives the secondary cell activation command sentby the base station or after SCell1 is activated, if the terminal findsthat a secondary TAT of SCell1 does not run, the terminal may initiate arandom access procedure to obtain the secondary TA of Scell. Theterminal uses PCell as a reference cell, that is, the terminal uses adownlink carrier of PCell for reference. When the terminal selects aPRACH of an uplink subframe n of SCell1 to send a preamble (preamble),the time when the preamble starts to be sent is the time when a downlinksubframe n corresponding to PCell starts to be received, where n may bea non-negative integer identifying a subframe or may be a symbol or acharacter that is used to identify the subframe.

S704. The terminal receives a message of the random access proceduresent by the base station and obtains a secondary TA.

The terminal receives the message 2 of the random access procedure sentby the base station, and obtains the secondary TA2 of Scell1 accordingto a TA carried in the message 2 of the random access procedure so thatthe secondary TAT of Scell may be started.

FIG. 9 is a schematic diagram of obtaining a secondary TA according toan embodiment provided in FIG. 8. FIG. 9 shows a method for calculatingTA2.

In FIG. 9, Msg1 is a message 1 of the random access procedure, where themessage 1 may include a preamble; and an eNB is an evolved base station(evolved NodeB).

TA2=TA_msg2+delta, or TA2=2×TA_msg2−TA_pcell, or TA2=TA_pcell+2×delta,where, TA_msg2 is a TA specified in the message 2 of the random accessprocedure; delta is a difference between a downlink carrier timing valueof a secondary cell and a downlink carrier timing value of a primarycell; and TA_pcell is a TA of the primary cell.

In the prior art, if the secondary TAT expires, the terminal may refreshbuffers (buffer) of all uplink hybrid automatic repeat requests (HybridAutomatic Repeat Request, HARQ), clear semi-statically scheduled uplinkand downlink resources, and notify a radio resource control (RadioResource Control, RRC) layer to release physical uplink control channel(Physical Uplink Control Channel, PUCCH) and/or sounding referencesignal (Sounding Reference Signal, SRS) resources. However, this maycause the PUCCH, SRS, and semi-statically scheduled resources to beincorrectly released, which further affects data transmission. Moreover,before the base station learns uplink out-of-synchronization of thesecondary cell, the base station may continue to schedule theout-of-synchronization secondary cell. As a result, resources arewasted, and uplink collision may occur due to the application of aninvalid secondary TA.

An embodiment of the present invention further provides a method forsolving the problems in the prior art where data transmission isaffected by incorrect releasing of the PUCCH, SRS, and semi-staticallyscheduled resources, and resource waste and uplink collision are causedby scheduling an out-of-synchronization secondary cell by the basestation. FIG. 10 is a flowchart of a method for processing uplinkout-of-synchronization according to the present invention. As shown inFIG. 10, the method specifically includes the following.

S801. A terminal starts a secondary TAT of a configured secondary cell.

S802. If the secondary TAT of the secondary cell expires, the terminalnotifies a base station, and/or stops uplink transmission on thesecondary cell, and/or activates the secondary cell.

In the embodiment of the present invention, the terminal may, forexample, obtain a secondary TA of the secondary cell according to theforegoing method embodiment of obtaining a secondary timing advance, sothat the secondary TAT of the secondary cell is started.

For example, the base station configures secondary cells SCell1 andSCell2 for the terminal, activates SCell1 and SCell2, and indicates, ina configuration message, that SCell1 and SCell2 belong to TAG2; and theterminal starts the secondary TAT of SCell1 and SCell2, that is, TAT2.If TAT2 expires, the terminal notifies the base station, and/or stopsall uplink transmission on SCell1 and SCell2, and/or deactivates SCell1and SCell2.

By using RRC signaling (which may be newly defined RRC signaling) or amedia access control component element (Media Access Control ComponentElement, MAC CE), or physical layer (Physical, PHY) signaling, theterminal may notify, on the primary cell or other secondary cell ofuplink synchronization, the base station that the uplinkout-of-synchronization occurs caused by TAT2 expiry. The terminal mayalso stop all uplink transmission, specifically including thetransmission of a physical uplink shared channel PUSCH, a physicaluplink control channel PUCCH, and a Sounding reference signal SRS, so asto avoid resource waste and possible uplink collision.

It should be noted that this method may be used in combination with themethod for obtaining a secondary timing advance according to theembodiment of the present invention, so as to save signaling overheadand system resources and avoid resource waste and possible uplinkcollision.

A person of ordinary skill in the art may understand that all or a partof the processes of the methods in the embodiments may be implemented bya computer program instructing relevant hardware or by a chip or aprocessor. The program may be stored in a computer readable storagemedium. When the program runs, the processes of the methods in theembodiments are performed. The storage medium may be a magnetic disk, anoptical disk, a read-only memory (Read-Only Memory, ROM), or a randomaccess memory (Read-Only Memory, RAM).

FIG. 11 is a structural schematic diagram of a terminal according to anembodiment of the present invention. The terminal provided in theembodiment of the present invention may be applied to the foregoingmethod embodiments of the present invention. As shown in FIG. 11, theterminal includes a receiving unit 11, a random access unit 12, and anobtaining unit 13.

The receiving unit 11 is configured to receive a secondary cellactivation command, where a secondary timing advance TA of a secondarycell is different from a primary TA of a primary cell.

The random access unit 12 is configured to initiate a random accessprocedure if a secondary time alignment timer TAT of the secondary celldoes not run after the receiving unit 11 receives the secondary cellrandom access command or after the secondary cell is activated.

The obtaining unit 13 is configured to obtain the secondary TA accordingto a TA received in the random access procedure.

After the receiving unit 11 receives the secondary cell activationcommand sent by a base station or after a secondary cell is activated,if the secondary TAT of the secondary cell does not run, the randomaccess unit 12 may initiate a random access procedure to obtain thesecondary TA of the secondary cell. The random access unit 12 mayimmediately initiate random access actively if the secondary TAT of thesecondary cell does not run after the receiving unit 11 receives thesecondary cell activation command sent by the base station or after thesecondary cell is activated. Or, the random access unit 12 may, insteadof actively initiating random access, initiate random access whentriggered by the base station, for example, the random access unit 12may initiate a random access procedure according to the random accesscommand after the terminal receives a random access command. Or, therandom access unit 12 may further determine random access according to aduration set by a set random access timer. If the terminal receives arandom access command within the duration set by the random accesstimer, the random access unit 12 may initiate random access according tothe reference cell specified in the random access command or initiaterandom access on a cell carrying the random access command; if a randomaccess command is not received within the duration set by the randomaccess timer, the random access unit 12 may use a secondary cell as areference cell and initiate random access on the secondary cell.

If a secondary cell that does not belong to the same TA group as theprimary cell has a PRACH resource, or at least one secondary cell amongmultiple secondary cells whose secondary TA does not belong to the sameTA group as the primary TA of the primary cell has a PRACH resource, therandom access unit 12 may use the secondary cell having a PRACH resourceas a reference cell and initiate a random access procedure on thesecondary cell.

The random access procedure initiated by the random access unit 12 maybe actively initiated, or initiated as triggered by the base station.The receiving unit 11 may further receive the random access command sentby the base station. For example, the random access unit 12 initiates arandom access procedure according to the received random access commandsent by the base station. The random access unit 12 may initiate,according to the specified reference cell, a random access procedure ona secondary cell having a PRACH resource, or may use a cell carrying therandom access command as a reference cell and initiate a random accessprocedure on the cell carrying the random access command. Additionally,the terminal may include a random access timer. If a random accesscommand sent by the base station is not received within the duration setby the random access timer, the random access unit 12 may still use thesecondary cell as a reference cell and initiate a random accessprocedure on the secondary cell. When random access is initiated on thesecondary cell, the secondary TA obtained by the obtaining unit 13 maybe a TA received in the random access procedure.

Additionally, the random access unit 12 may also use the primary cell asa reference cell and initiate a random access procedure on the secondarycell. In this case, the secondary TA obtained by the obtaining unit 13may not be a TA sent by the base station in the random access procedure;the secondary TA obtained by the terminal may be a sum of the secondaryTA sent by the base station, which is a TA received in the random accessprocedure, and a difference between a downlink carrier timing value of asecondary cell and a downlink carrier timing value of a primary cell.Or, the secondary TA obtained by the obtaining unit 13 may be adifference between twice the TA received in the random access procedureand the TA of the primary cell.

When none of the secondary cells of the terminal has a PRACH resource,the random access unit 12 may still use the secondary cell as areference cell and initiate a random access procedure on the primarycell. In this case, the secondary TA obtained by the obtaining unit 13may be a sum of the TA sent by the base station in the random accessprocedure and a difference between a downlink carrier timing value ofthe secondary cell and a downlink carrier timing value of the primarycell; or, the secondary TA obtained by the obtaining unit 13 may be adifference between twice the TA received in the random access procedureand the TA of the primary cell.

In the embodiment, after the terminal receives a secondary cellactivation command sent by the base station or after a secondary cell isactivated, the terminal initiates a random access procedure to obtain asecondary timing advance, thereby saving signaling overhead and systemresources.

FIG. 12 is a structural schematic diagram of a terminal according toanother embodiment of the present invention. The terminal provided inthe embodiment of the present invention may be applied to the foregoingmethod embodiments of the present invention. As shown in FIG. 12, theterminal includes a receiving unit 11, a random access unit 12, and anobtaining unit 13.

Further, the random access unit 12 is specifically configured to use asecondary cell as a reference cell and initiate a random accessprocedure on the secondary cell.

The receiving unit 11 is further configured to receive a random accesscommand sent by a base station.

If the random access command received by the receiving unit 11 specifiesa reference cell, accordingly, the random access unit 12 may beconfigured to initiate a random access procedure on the secondary cellaccording to the reference cell specified in the random access command.

The random access unit 12 is further configured to use a cell carryingthe random access command as a reference cell and initiate a randomaccess procedure on the cell carrying the random access command.

The terminal provided in the embodiment may further include a randomaccess timer 14, which is started after the receiving unit 11 receives asecondary cell activation command sent by the base station or after thesecondary cell is activated.

The random access unit 12 is specifically configured to: if a randomaccess command sent by the base station is not received within aduration set by the random access timer 14, use a secondary cell as areference cell and initiate a random access procedure on the secondarycell.

The secondary TA obtained by the obtaining unit 13 is a TA received inthe random access procedure.

The random access unit 12 is further configured to use the primary cellas a reference cell and initiate a random access procedure on thesecondary cell; or, use the secondary cell as a reference cell andinitiate a random access procedure on the primary cell.

Accordingly, the secondary TA obtained by the obtaining unit 13 is a sumof the TA received in the random access procedure and a differencebetween a downlink carrier timing value of the secondary cell and adownlink carrier timing value of the primary cell; or, is a differencebetween twice the TA received in the random access procedure and the TAof the primary cell.

The random access unit 12 is further configured to, during initiation ofthe random access procedure, use the downlink carrier of the referencecell for reference when sending a preamble.

The terminal provided in the embodiment of the present invention mayfurther include a starting unit 15 and a processing unit 16.

The starting unit 15 is configured to start a secondary TAT according tothe secondary TA obtained by the obtaining unit 13.

The processing unit 16 is configured to: if the secondary TAT expires,notify the base station that the secondary TAT expires, and/or stopuplink transmission on the secondary cell corresponding to the secondaryTAT, and/or deactivate the secondary cell corresponding to the secondaryTAT.

The embodiment of the present invention may further provide a terminalthat includes the starting unit 15 and the processing unit 16 shown inFIG. 12. The terminal may obtain the secondary TA of the secondary cellby using the method for obtaining a TA according to the embodiment ofthe present invention.

On the basis of the previous embodiment, a random access timer 14 may beset. If the receiving unit 11 does not receive a random access command,which is sent by the base station, within a duration set by the randomaccess timer 14, the random access unit 12 may still use the secondarycell as a reference cell and initiate a random access procedure on thesecondary cell or another secondary cell that shares the same secondaryTA with the secondary cell and has a PRACH resource. In this case, theTA received by the obtaining unit 13 in the random access procedure andis sent by the base station is a secondary TA.

The terminal provided in the embodiment of the present invention is adevice that executes the method for obtaining a secondary timing advanceaccording to embodiments of the present invention and corresponds to themethod for obtaining a secondary timing advance according to embodimentsof the present invention. For the specific process for the terminal toexecute the method for obtaining a secondary timing advance, referencemay be made to the method embodiments, and details are not providedherein.

In the embodiment of the present invention, after the terminal receivesthe secondary cell activation command sent by the base station or afterthe secondary cell is activated, the terminal initiates a random accessprocedure to obtain the secondary timing advance, thereby savingsignaling overhead and system resources.

FIG. 13 is a structural schematic diagram of a base station according toan embodiment of the present invention. The base station provided in theembodiment of the present invention may be applied to the foregoingmethod embodiments of the present invention. As shown in FIG. 13, thebase station includes a first sending unit 21 and a second sending unit22.

The first sending unit 21 is configured to send a secondary cellactivation command to a terminal.

The second sending unit 22 is configured to send a TA to the terminal ina random access procedure according to random access initiated by theterminal, where the random access is initiated by the terminal if asecondary TAT of a secondary cell does not run after the terminalreceives the secondary cell activation command or after it is confirmedaccording to the secondary cell activation command that the secondarycell is activated; and the secondary TA of the secondary cell isdifferent from a primary TA of a primary cell.

In this embodiment, a TA is sent to the terminal through the secondsending unit 22 so that the terminal may obtain a secondary TA.

The first sending unit 21 is further configured to send a random accesscommand to the terminal before the terminal initiates a random accessprocedure, so that the terminal uses a cell carrying the random accesscommand as a reference cell and initiates a random access procedure onthe cell carrying the random access command; if the random accesscommand specifies a reference cell, the terminal initiates a randomaccess procedure on the secondary cell according to the reference cellspecified in the random access command.

The TA sent to the terminal in the random access procedure is thesecondary TA.

The first sending unit 21 is further configured to send a random accesscommand to the terminal before the terminal initiates a random accessprocedure, so that the terminal uses the primary cell as a referencecell and initiates a random access procedure on the secondary cell, orso that the terminal uses the secondary cell as a reference cell andinitiates a random access procedure on the primary cell.

In this embodiment, the terminal may be a terminal provided inembodiments shown in FIG. 11 and FIG. 12.

The base station provided in the embodiment of the present invention isa device that executes the method for obtaining a secondary timingadvance according to embodiments of the present invention andcorresponds to the method for obtaining a secondary timing advanceaccording to embodiments of the present invention. For the specificprocess for the base station to execute the method for obtaining asecondary timing advance, reference may be made to the methodembodiments, and details are not provided herein.

In the embodiment of the present invention, after a secondary cellactivation command sent by the base station is received or after asecondary cell is activated, the base station initiates a random accessprocedure to obtain a secondary timing advance, thereby saving signalingoverhead and system resources.

Finally, it should be noted that the foregoing embodiments are merelyintended for describing the technical solutions of the present inventionother than limiting the present invention. Although the presentinvention is described in detail with reference to the foregoingembodiments, a person of ordinary skill in the art should understandthat modifications may still be made to the technical solutionsdescribed in the foregoing embodiments, or equivalent replacements maybe made to some technical features thereof, without departing from thescope of the technical solutions of the embodiments of the presentinvention.

What is claimed is:
 1. A method for obtaining a secondary timing advance(TA), the method comprising: initiating, by a terminal, a random accessprocedure, when a secondary cell is activated and a secondary timealignment timer (TAT) of the secondary cell does not run; and obtaining,by the terminal, a secondary TA of the secondary cell according to a TAreceived by the terminal in the random access procedure; wherein thesecondary TA of the secondary cell and a primary TA of a primary cell donot belong to a TA group.